1. Field of the Invention
This invention relates generally to the field of material testing, and more specifically to a method and system for measuring properties of a non-Newtonian fluid, such as an asphalt binder.
2. Description of the Related Technology
The word asphalt generally refers to any one of a number of different viscous bituminous substances that can be used for paving or road making The viscous asphalt material is typically used to bind aggregate materials such as crushed stone in order to form a paved surface.
Thermal shrinkage cracking in asphalt pavement occurs when the thermal tensile stress within the asphalt pavement that results from temperature drop exceeds the strength at that temperature. Historically, low temperature thermal cracks have been controlled by limiting the asphalt binder stiffness. Assuming similar asphalt binder tensile strengths and coefficients of thermal expansion/contraction, the binders with a higher stiffness will crack at a higher temperature than softer binders. Because an accurate and easy to use measuring instrument was not available, the cracking temperature or the limiting low temperature stiffness of asphalt binder had been extrapolated from consistencies measured at higher temperatures, such as penetrations at 5 and 25° C., viscosity at 25° C., or ring-and-ball softening point (50-60° C.). Hill, J. F., Inst. Petroleum, vol. 74-014 (1974) and Van der Poel, C., Journal of Applied Chemistry, vol. 4, 221-236 (1954).
In the United States, the Association of American State Highway and Transportation Officials (AASHTO) has published and implemented a series of performance graded (“PG”) binder specifications. Low-end temperatures of PG grading are typically determined by utilizing one or more of several known systems including the Bending Beam Rheometer (BBR) and/or the Direct Tension Tester (DTT). While effective at generating useful data, these systems are complex, require the performance of numerous calculations, require the testing of many specimens, do not directly measure the temperature at which the specimen fails, and are often very time consuming and expensive to perform.
A need accordingly exists for a system and method for measuring the properties of a non-Newtonian fluid that is less time-consuming and expensive than conventional systems and methods.